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East Butte: A volcanic dome of the Eastern Snake River Plain, IdahoPreliminary mapping shows East Butte to be a single, large cumulo-dome composed dominantly of rhyolite which can be classified into three main groups based on color and structure. The rhyolite of East Butte is aphanitic with phenocrysts of sanidine and quartz which vary from 1 to 5 mm in length. Vesicular reddish black inclusions of basalt up to 10 cm in length, found in all varieties of the East Butte rhyolites are believed to have originated from fragmentation of the basalt walls of the conduit by rhyolitic magma as it was emplaced. Most of the inclusions contain plagioclase phenocrysts. These phenocrysts measure up to 1 to 2 cm in length and have a typical euhedral, tabular habit. A 250-m diameter depression which has the appearance of a crater is located at the top of East Butte. Evidence supporting the fact that the depression is a crater is displayed by three small (3 to 5 m in height) mounds of massive rhyolite which border the depression.
Document ID
19840015407
Acquisition Source
Legacy CDMS
Document Type
Other
Authors
Bretches, J. E.
(State Univ. of New York Buffalo, NY, United States)
King, J. S.
(State Univ. of New York Buffalo, NY, United States)
Date Acquired
August 12, 2013
Publication Date
January 1, 1984
Publication Information
Publication: NASA, Washington Rept. of Planetary Geol. Program, 1983
Subject Category
Geophysics
Accession Number
84N23475
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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